1. Field of the Invention
The present invention relates to a technology for temporarily stopping the combustion in some cylinders of an internal combustion engine for a vehicle, and also, for holding at least one of an intake valve and an exhaust valve of each cylinder in which the combustion is temporarily stopped, at a low valve lift amount state or at a valve closing state. In particular, the present invention relates to a technology for reducing torque variation due to uneven explosion intervals at the time when the combustion is temporarily stopped in some cylinders (to be referred to as some cylinder operations temporarily stopping time, hereunder).
2. Description of the Related Art
In an internal combustion engine disclosed in Japanese Laid-open (Kokai) Patent Application Publication No. H7 (1995)-189757, in a low load operating region, in order to reduce a pumping loss, the combustion is temporarily stopped in some cylinders. As a result, torque variation due to an inertia force of a piston system is reduced, so that the vibration of the internal combustion engine is reduced.
Further, in an internal combustion engine disclosed in Japanese Laid-Open (Kokai) Patent Application Publication No. S61 (1986)-65023, when all cylinders are operated (to be referred to as all cylinders operating time, hereunder), a torque is applied to a crankshaft using a motor/generator, to reduce torque variation due to an explosion force of the internal combustion engine and torque variation due to an inertia force of a piston system.
However, in the internal combustion engine disclosed in Japanese Laid-open (Kokai) Patent Application Publication No. H7-189757, at some cylinder operations temporarily stopping time, the torque variation occurs as a result that the explosion and combustion at each constant crank angle cannot be maintained, and also, the torque variation occurs by the torque, which prevents the rotation of the crankshaft (to be referred to as a negative torque, hereunder) and is applied to the crankshaft in an expansion stroke of each cylinder in which the combustion is temporarily stopped. Such torque variation is called torque variation due to uneven explosion intervals. Thus, even in the internal combustion engine disclosed in Japanese Laid-open (Kokai) Patent Application Publication No. H7-189757, the torque variation due to the uneven explosion intervals cannot be reduced, and accordingly, the reduction in the vibration of the interval combustion engine might be insufficient.
Further, in Japanese Laid-Open (Kokai) Patent Application Publication No. S61-65023, there is not especially disclosed a control of the motor/generator at some cylinder operations temporarily stopping time.